It is well known that hydraulic motors and pumps which have vane elements in both the rotor and stator under certain conditions can have interference problems as the rotor vanes and the stator vanes cross each other. These problems become more acute at higher speeds and/or higher loading. Various improvements have been suggested in the past to avoid the destructive detenting of the stator and rotor vanes with respect to each other and their slots in order to prevent vane locking, detenting, and minimizing wear. In U.S. Pat. No. 3,782,867, rotor and stator vanes having different thicknesses are provided with hydraulic and spring loading. In U.S. Pat. No. 3,957,404, improvements in the shape and size of the rotor and stator vane tips are disclosed. Thicker vanes, when they cross a thinner vane, are less likely to catch in the slot of the thinner vane. However, the thicker vane can lose its biasing pressure or can wear and allow the thinner vane to enter into and catch in the slot of the thicker vane. Another prior art solution was to make the thicker vane have the same depth as its vane slot so that it could not retract far enough into its slot to allow the thinner vane to enter the slot of the thicker vane. However, this required that the bottom of the thicker vane slot be flat and created manufacturing difficulties. Still the outer end of the thicker vane could wear and allow the thinner vane to catch. Therefore, in spite of all of the suggested solutions, the problem of destructive detenting of the stator and rotor vanes with respect to each other and their respective slots has not been entirely solved and remains a problem particularly at high loads, high speeds, and overrunning.
The present invention is directed to shaping the vane slots of one or both of the rotor and stator for preventing the catching of the opposing vanes in the vane slots.